1. Field of the Invention
The present invention relates to a tool for tightening a revolving tightening member, such as a nut and bolt or a nut on a chucking device for machine tools, and in particular, to a wrench which can easily be attached to the tightening member.
2. Description of the Related Art
In the past, various kinds of tighteners such as nuts and bolts which are tightened when revolved around an axis have been known. Generally, edges are provided on the outer surface of the tightening member by, for example, forming the tightening member into a prismatic shape, such as a hexagon. A wrench or other tool comprising an open end to fit the shape of the tightening member can be attached to grasp the outer surface edges of the tightening member. By revolving the tool, the tightening member can be tightened.
The above-mentioned mechanism can also be used for tightening nuts on chucking devices or cutting tool holders, i.e., the outer surface of the tightening nut is knurled, and a recess or engagement groove is formed to receive the wrench.
However, placing a wrench to the edges or engagement grooves of the nut is both time consuming and burdensome. Moreover, the manufacturing process for the nuts is made more complex, as recesses and grooves on the tightening member must be formed, or the tightening member must be formed in an edged shape.
Moreover, the relative angle of the wrench enabling it to connect with the edges or grooves of the nut is so limited that if the space around the nut is insufficient, the wrench may not be able to connect to the nut, depending on the angle of the nut.